I mean you have signed a contract requiring you to be at work at 7. So that's when you have to be there, unless you want to be sacked. With an hourly or monthly wage the company is paying for your time and they expect you to put in that time. It'd be different if you had a contract by tender or piecework contract, not sure of the correct English language term. If you have that, you can often set your own hours (to a degree) as long as the job gets done. But that's not what most people have in their employment contract.

Other side of the coin to slacking from the required work time would be if the employer would be slacking from the required pay. And that does happen too and is even worse. But the contract should bind both sides to it so neither happens.